The invention relates to a discharge device for bulk containers for particulate bulk materials, particularly powders and granules, preferably using a blow-through rotary valve, and its use, i.e. a process for discharging the bulk container.
Particulate bulk materials such as powders and granules are extensively transported in bulk containers from manufacturer to user and discharged at the user's premises. In the following description, bulk containers are intended to mean both bag-shaped containers, such as so-called bulk bags with a filling volume of a few hundred liters to several m.sup.3, and silos and other container-shaped bags with or without a bag-shaped inlet with a filling volume of 5 to 50 m.sup.3, particularly 10 to 30 m.sup.3. The container-shaped large bags are conventionally fixed to the cargo bed of a road or rail vehicle in such a way that the contents can be discharged by opening the container's discharge opening located on one side and tilting the vehicle's cargo bed.
According to a known embodiment for discharging such bulk containers, particularly large bags with an inlet, a discharge device in connection with the bulk container is coupled to a blow-through rotary valve. In the simplest case, the discharge device can be the discharge provided by the container-inlet. By starting the motor for the cellular wheel of the blow-through rotary valve and supplying delivery gas, generally compressed air, to the blow-through part of the rotary valve, bulk material falling into the rotary valve is pneumatically fed to the destination, such as a stationary silo or reaction tank, via a delivery line. The main problem of a discharge device of this kind lies in the venting of the leakage air arising because of the excess pressure in the blow-through part of the rotary valve and of the compressed air conveyed with the cellular wheel to the product feeds Inadequate venting blocks the product feed and hence the discharge process because of air pockets which are formed.
To solve the inadequate venting, a vent connection arranged on the rotary valve has been connected hitherto to the internal chamber of the bulk container by a hose; if an inlet is present, the hose reaches into the inlet. Depending on the delivery pressure required and the particle size of the bulk material, however, considerable operational difficulties are encountered in the course of discharge: as the pressure increases, the container and/or the inlet are subject to excess pressure so that delivery air may be pressed out of the container and/or inlet and a great deal of dust created thereby on the outside.